1. Field of the Invention
The present invention relates generally to a horizontal deflection coil for a deflection yoke used in a cathode ray tube, and more particularly to a horizontal deflection coil for a deflection yoke, which is provided with a section for correcting inner pincushion distortion, thereby removing the need for another circuit for correcting the inner pincushion distortion.
2. Description of the Prior Art
Recently, the market trend for display apparatuses pursues flatness, large size, high-resolution, low power consumption, and slimness that enables installation space to be reduced and the efficiency of use of space to be increased.
A computer monitor that is one of such display apparatus has been developed in pursuit of flatness, large size, high-resolution, low power consumption and slimness. Particularly, high quality display apparatuses, in which power consumption is reduced and effective screens are large-sized, are required to follow stringent environmental regulations.
The monitor market has been developing at 10% annually, and is divided into a Cathode Ray Tube (CRT) monitor market and a Liquid Crystal Display (LCD) monitor market.
However, with rapid progress of relevant technologies, the LCD monitor market has been developing at 50% annually, compared to the CRT monitor market. Accordingly, in this situation, CRT monitors are required to improve their quality and have competitive power in order to compete with LCD monitors.
The maximum share of the CRT monitor market is occupied by 17xe2x80x3xcx9c19xe2x80x3 flat screen monitors to meet the market trend toward large sizes and flatness.
FIG. 1 shows an example of a conventional CRT, which shows a conventional curved screen CRT.
The conventional curved screen CRT includes a convex screen panel 1 that is curved outward at its front surface, a funnel 2 that is attached to the back end of the screen panel 1 using frit glass and maintains the inside of the CRT in a vacuum state, an electron gun 5 that is mounted in a neck 7 positioned at the rear of the funnel 2 and irradiates electron beams 4a, 4b and 4c, and a deflection yoke 6 that deflects the electron beams 4a, 4b and 4c irradiated from the electron gun 5 in left, right, up and down directions.
The deflection yoke 6 is used to apply horizontal and vertical deflection magnetic fields to the neck 7 of the CRT. The deflection yoke 6 includes a vertical deflection coil (not shown) that vertically deflects the electron beams 4a, 4b and 4c by applying the vertical deflection magnetic field to the electron beams 4a, 4b and 4c irradiated from the electron gun 5 of the CRT, a horizontal deflection coil (not shown) that horizontally deflects the electron beams 4a, 4b and 4c by applying the horizontal deflection magnetic field to the electron beams 4a, 4b and 4c irradiated from the electron gun 5 of the CRT, a separator (not shown) that precisely separates the horizontal deflection coil from the vertical deflection coil and electrically insulates the horizontal deflection coil from the vertical deflection coil, and a ferrite core (not shown) that enhances magnetic fields applied by the horizontal and vertical deflection coils.
The horizontal deflection coil and the vertical deflection coil are arranged to be perpendicular to each other in order to apply horizontal and vertical deflection magnetic fields to the electron beams 4a, 4b and 4c irradiated from the electron gun 5.
In such a curved screen CRT monitor, the screen panel 1 is curved to be protruded outward, deflection distances between the deflection yoke 6 and the fluorescent surface of a screen do not greatly differ from each other in the upper, middle and lower portions of the screen, so that distortion is limitedly generated.
That is, as shown in FIG. 1, in the conventional curved screen panel 1, a deflection distance A of the electron beam 4a irradiated onto the upper portion of the screen, a deflection distance B of the electron beam 4b irradiated onto the middle portion of the screen and a deflection distance C of the electron beam 4c irradiated onto the lower portion of the screen do not greatly differ from each other, so that distortion is limitedly generated.
However, the recent display market trend pursues flatness of a screen, whose panel is constructed to be flat, as described above, so that a screen panel 11 is formed to be flat, as shown in FIG. 2.
A CRT provided with the flat screen panel 11 has various merits compared to the conventional curved screen monitor, while the CRT has a defect of increased distortion characteristics.
That is, since the screen panel 11 is flat, as shown in FIG. 2, a deflection distance Axe2x80x2 of the electron beam 14a irradiated onto the upper portion of the screen, a deflection distance Bxe2x80x2 of the electron beam 14b irradiated onto the middle portion of the screen and a deflection distance Cxe2x80x2 of the electron beam 14c irradiated onto the lower portion of the screen differ from each other, so that distortion is generated.
As the deflection distances Axe2x80x2, Bxe2x80x2 and Cxe2x80x2 differ from each other, an inner pincushion phenomenon resulting from distortion is generated in the front surface of the screen as shown in FIG. 3.
In general, a picture is formed by a deflection yoke that forms a pincushion-shaped magnetic field using a horizontal deflection coil and a barrel-shaped magnetic field using a vertical deflection coil. The inner pincushion phenomenon almost does not appear due to the curvature of the CRT in a general curved screen panel, or is invisible to the naked eye when it appears in the curved screen panel.
However, it is found that the inner pincushion phenomenon appears in a flat CRT because vertical pincushion distortion is incompletely corrected in a central portion of an area between the central portion and each side end of the screen.
The inner pincushion phenomenon is pincushion distortion in which a picture displayed on the CRT becomes curved inward in a central portion of an area between the central portion and each side end of the screen as indicated by solid lines shown in FIG. 3.
That is, the vertical lines of the screen should appear as straight lines to connect the upper, middle and lower portions of the screen as indicated by dotted lines shown in FIG. 3. However, if the inner pincushion phenomenon described above is generated, a picture seems to be curved inward, so that the quality of the screen is decreased and high quality of the CRT may not be offered.
Accordingly, an additional circuit is used in the deflection yoke to improve the inner pincushion phenomenon, and the circuit is referred to as an inner pincushion correction module.
The inner pincushion correction module is an additional circuit that may remove pincushion distortion in order to correct the vertical pincushion distortion, which is caused by horizontal deflection coils that forms a pincushion-shaped magnetic field.
The inner pincushion correction module is operated by an induced electromotive force caused by a mutual inductance between vertical and horizontal deflection coils.
An example of the conventional inner pincushion correction module is shown in FIG. 4, and is described with reference to FIG. 4.
Two horizontal correction coils L3 and L4 are wound to generate reverse magnetic fields, and permanent magnets 19 and 20 for apply a fixed deflection magnetic field to the horizontal correction coils L3 and L4 and a vertical correction coil L7 are disposed.
The horizontal correction coils L3 and L4 receive the fixed deflection magnetic field applied by the permanent magnets 19 and 20. The size of the central portion of the screen becomes small and the sizes of the corners of the screen become identical by the action of the vertical correction coil L7, so that left and right pincushion distortions are corrected.
If current flows into the horizontal correction coils L3 and L4, as shown in FIG. 4, a magnetic field is generated by the left horizontal correction coil L3 in the direction opposite to that of the fixed deflection magnetic field, and another magnetic field is generated by the right horizontal correction coil L4 in the direction identical to that of the fixed deflection magnetic field.
In this case, the direction of the magnetic field generated by the left horizontal correction coil L3 is opposite to that of the fixed deflection magnetic field by the action of the permanent magnets 19 and 20.
The inner pincushion correction module constructed as described above is operated by an induced electromotive force caused by a mutual inductance between the vertical and horizontal correction coils L7, L3 and L4, so that horizontal correction coils L3 and L4 form a pincushion-shaped magnetic field, thereby correcting the vertical pincushion distortion.
However, a conventional flat screen CRT is disadvantageous in that a separate inner pincushion correction module should necessarily be used to correct, the inner pincushion distortion.
For this reason, the manufacturing cost of the flat screen CRT is increased due to an increase in number of assembly steps required to attach the inner pincushion correction module to the deflection yoke, as well as an increase in number of parts required to manufacture the inner pincushion correction module.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a deflection yoke, which corrects inner pincushion distortion using a horizontal deflection coil constituting the deflection yoke, without using an inner pincushion correction circuit.
In order to accomplish the above object, the present invention provides a horizontal deflection coil for a deflection yoke including an inner pincushion improving section connected to a screen bent, and sub-sections connected to the inner pincushion improving section, wherein the inner pincushion improving section is disposed in an angular range of 45 to 60 degrees, and the sub-sections include a horizontal color registration improving section for preventing a horizontal component of a green color from being widened, and a vertical color registration improving section for preventing a vertical component of the green color from being widened.
Preferably, the HCR improving section may be connected at its first screen-side end to the screen bent and connected at its second end to the inner pincushion improving section, and the VCR improving section may be connected at its first screen-side end to a position where the inner pincushion improving section and the screen bent are connected to each other and connected at its second end to another adjacent section.
Preferably, the HCR improving section may be connected at the second end to a position corresponding to one-half to two-thirds of a length of the inner pincushion improving section.
Preferably, the VCR improving section may be formed to be parallel to the HCR improving section.
Preferably, the number of turns of wires of the inner pincushion improving section may be greater than the sum of the numbers of turns of wires of HCR and VCR improving sections.
In addition, the present invention provides a deflection yoke including a horizontal deflection coil provided with an inner pincushion improving section, a HCR improving section for preventing a horizontal component of a green color from being widened, and a VCR improving section for preventing a vertical component of the green color from being widened, the HCR and VCR improving sections being sub-sections, wherein a inner pincushion correction module for correcting inner pincushion is omissible.